Work

Petrogenesis of the Early Cretaceous volcanic-intrusive complex in northern North China Craton: Implications for crustal magma system evolution

Year: 2024

Type: article

Abstract: Identifying the origin and evolution of silicic magma is crucial for elucidating the transcrustal magmatic system and the evolution of continental crust . The Early Cretaceous volcanic-intrusive complex in the Kulongshan area provides an important insight into the evolution of silicic magma. Zircon U Pb dating indicates that these spatially associated rocks formed between 140 and 131 Ma. The volcanic and subvolcanic rocks and alkali feldspar–alkaline granites are high silica (SiO 2 = 75.79–77.89 wt%) and alkali-rich and demonstrate strong negative Eu anomalies (Eu/Eu* = 0.02–0.06), as is typical of A-type rocks. Significant geochemical discontinuities were found between the potassium (K)-feldspar granite porphyry (SiO 2 = 67.86–70.80 wt%, Eu/Eu* = 0.20–0.44) and the high-silica rocks. These rocks exhibit ε Hf (t) and T DM2 values ranging from −18.1 to −9.2 and 2.34 to 1.84 Ga, respectively, indicating that the magmas originated from partial melting of the Paleoproterozoic continental crust. The geochemical characteristics show that the high-silica volcanic and subvolcanic rocks, along with the alkali-feldspar–alkaline granites, display a distinct trend of fractional crystallization . The K-feldspar granite porphyry exhibits distinct characteristics of feldspar accumulation. The consistent material source of the Kulongshan volcanic-intrusive complex suggests that the magma may have ascended from the source area, leading to magma interaction in the deep magma reservoir , followed by fractional crystallization in the shallow magma reservoir. The results indicate that Early Cretaceous high-silica rocks were formed via the extraction and coalescence of interstitial melts within the magma reservoir, with the K-feldspar granite porphyry representing residual crystal accumulation.

Source: Lithos

DOI: 10.1016/j.lithos.2024.107924